Year	Number
1970	4675793
1971	4954679
1972	5282262
1973	5606977
1974	5914082
1975	6311525
1976	6598134
1977	6841648
1978	7167547
1979	7337632
1980	7875702
1981	8413308
1982	9090942
1983	9976348
1984	10900000
1985	11700000
1986	11500000
1987	12000000
1988	12300000
1989	12400000
1990	12900000
1991	13800000
1992	14700000
1993	14800000
1994	15100000
1995	15500000
1996	15700000
1997	15900000
1998	16200000
1999	16500000
2000	17100000
2001	18100000
2002	18900000
2003	19800000
2004	21300000
2005	21900000
2006	23400000
2007	24000000
2008	25300000
2009	26400000
2010	28000000
2011	29000000
2012	30200000
2013	33000000
2014	31700000
2015	33400000
2016	33300000
2017	33800000
2018	35100000